Legumes play a crucial role in supplying essential proteins for both food and feed purposes. They are commonly integrated into agricultural practices because of their beneficial influence on soil fertility. This can be attributed to their remarkable capacity for biological nitrogen fixation (BNF), a symbiotic relationship with microorganisms like rhizobia that enables them to convert atmospheric nitrogen into usable forms (Fujita et al., 1992). In order to maximize the utilization of this process, integrated cropping systems such as crop rotation, intercropping, improved fallows, green manuring, and alley cropping are commonly employed (Kebede, 2021). As illustrations, in the dry savanna of West Africa, the integration of soybean and its residues into cereal crops within a crop rotation system has been reported to result in nitrogen contributions ranging from 38 to 126 kg N ha-1 (Sanginga et al., 2003), similarly in South Africa, the introduction of different legumes into maize crop rotation systems has yielded nitrogen contributions ranging from 32 to 83 kg N ha-1 (Lengwati et al., 2020); Regarding intercropping or mix cropping system, the action of rhizodeposition of legumes advances the companion crops (Fustec et al., 2010), this occurs in two ways: in the short term through direct nitrogen transfer and in the long term through the mineralization of residues (Murphy-Bokern et al., 2017); For the improved fallows, it is an effective strategy for restoring soil fertility by introducing beneficial legume crops during the fallow period. This involves planting fast-growing legume tree or shrub species as substitutes for traditional fallows, allowing the benefits of fallow practices to be realized in a shorter timeframe. This approach accelerates the restoration of soil fertility by harnessing the advantages of fallow systems within a condensed period. In legume tree fallows, the wood can be selectively harvested, while the nitrogen-rich components such as leaves, pods, and green stems serve as valuable sources of nutrients that contribute to soil fertility enhancement (Sanchez, 1999), according to Nair et al., the presence of a one-year fallow of Sesbania sesban resulted in a yield improvement of 50-80% for subsequent maize crops. Furthermore, two-year fallows demonstrated even greater yield increases ranging from 150-270% (Nair et al., 1999); The green manure or non-decomposed plant matter, especially legume, either on the soil surface (as seen in conservation agriculture) or tilled into the soil. The primary objective is to enrich the soil with nutrients through the decomposition of biomass (Fageria, 2007), for instance, incorporating Leucaena into the soil at a rate of 6 t ha-1 year-1 before sowing rice and wheat resulted in a contribution of approximately 80 kg of organic nitrogen (N) ha-1 year-1. This level of organic nitrogen can effectively replace 25% of mineral nitrogen fertilizers (Gangwar et al., 2004); Lastly, the alley cropping which is a farming practice where crops are grown in rows or alleys formed by strategically planting trees or shrubs, this approach helps to restore soil fertility and improve overall productivity (Da Costa Leite et al., 2019). Through the implementation of this practice, nitrogen yields typically range from 200 to 300 kg ha-1, with approximately 50% of the nitrogen obtained from the atmosphere (Kebede, 2021).
REFERENCES
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